Traditional hip replacement surgery has been used in the United States since as early as the 1960's. The surgical technique to implant a hip has not drastically changed over the years, and today, this technique is quite successful. In fact, the surgical technique is prolifically used throughout the world and has a known success rate of over 90%. Certainly, the traditional surgical technique is fundamentally sound and predictable.
Unfortunately, traditional techniques to implant a hip have well recognized shortcomings. Most importantly, a rather large incision is made on the side of the hip. The incision can extend from 6 to 12 inches; the actual length of the incision depends on the size of the patient and type of surgery (revision versus total hip arthroplasty, for example). A long, deep incision can divide a number of important stabilizing muscles and tendons and further damage the hip joint and surrounding soft tissue. Inevitably, long incisions lead to larger blood losses, longer rehabilitation times for patients, and unsightly scar lines. A patient can easily spend four or five days in the hospital after a total hip arthroplasty, for example.
Recently, surgeons have been developing new, less invasive surgical techniques to perform total hip arthroplasty and revision hip surgery. Minimally invasive surgery, or MIS, is one such technique with great promise to become a popular and accepted technique for implanting a hip.
MIS has significant advantages over traditional hip replacement surgery. Most importantly, a rather small incision is made on the side on the hip. This incision is approximately 3 to 5 inches long, and the benefits of a shorter incision are enormous.
First and foremost, the patient can recover in a much shorter period of time after a MIS. The recuperation time in the hospital can be a few days and significantly reduce the cost to both the patient and hospital. In fact, some patients are leaving the hospital within 24 to 48 hours after the surgery. Obviously, this shortened time period is extremely important to the patient.
As another advantage, MIS is less invasive and traumatic to the patient. Significantly less soft tissue is disrupted in a minimally invasive surgery compared to a traditional hip surgery. Also, the amount of blood loss is reduced, and patients will require fewer blood transfusions. Further, the length of the scar is significantly smaller, and these scars are more cosmetically appealing. The incisions themselves heal in a much shorter period of time and are much less painful than a long ten or twelve inch incision. As such, the patient can sooner return to work or enjoy recreational activities. In short, the patient can more quickly return to a normal way of life.
Presently, instruments to perform MIS are being developed and refined. These instruments have a vital role in the ability to perform a successful minimally invasive surgery. These instruments, for example, must enable the surgeon to place the hip implant in a very precise location. If the implant is not accurately placed, then complications, such as dislocation or subluxation, can occur. Further and most importantly, the instruments must consistently and reliably perform through a small three inch opening in the patient.
A successful design of instruments for MIS has other challenges as well. Specifically, the instrument must be easy to use and facilitate the implantation procedure. If the MIS instrumentation is too cumbersome or not easy to manipulate, then the surgeon will be less likely to use minimally invasive surgery. The patient, then, will not reap the benefits MIS has to offer.
As yet another consideration, MIS instrumentation must appeal to a wide range of orthopedic surgeons with various skills and experience. If, for example, the instruments are too complex and complicated, then they will not be appealing and accepted in the orthopedic surgical community. Further yet, the training and skill level required to use the instruments and become proficient with them, cannot be overly taxing on the orthopedic surgeons.
While implanting or repairing a prosthetic acetabular shell in MIS for instance, screw-hole plugs and dome plugs must be screwed in the acetabular shell. Further, bone screws must be driven through screw-holes in the acetabular shell and into surrounding cortical bone to secure the shell to this bone. Traditional surgical driving instruments, though, are not shaped and sized to engage a screw-hole plug or bone screw and place it through the acetabular shell. For one reason, the screw-hole openings in the acetabular shell are at an angle with respect to the surgical site. Further, these screw-hole openings are deep in the surgical site and relatively far from the entrance of the incision. Thus, a straight driving instrument will not have the proper angulation to reach the screw-hole opening in the shell. Further, a short driving bit attached to the end of a driving instrument will not be able to reach the screw-hole openings.
Great care must be taken while placing a screw-hole plug or dome plug in the acetabular shell. If the threads on the plug do not properly align with the threads in the shell, then these threads can become stripped or cross-threaded. In such instances, the acetabular shell may have to be removed and replaced during the surgical procedure. Further yet, great care must be taken while placing a bone screw through the screw-hole opening in the acetabular shell. If the bone screw is not placed with the correct angle, then the bone screw may not seat well in the screw-hole opening. Additionally, the bone screw may not properly engage cortical bone to hold the shell in place in the acetabulum. Further yet, if the driving bit is not long enough, then the bone screw may not be placed deeply enough into the acetabulum.
In short, instruments, and in particular driving instruments and driving bits attachable to screw-hole plugs and bone screws, play a vital role in MIS surgery for hip implantation. It therefore would be advantageous to provide a new method and accompanying instruments for driving and aligning screw-hole plugs and bone screws in minimally invasive surgery to implant a prosthetic hip.